1. Field of the Invention
The present invention relates to a decoding circuit decoding a data stream coded by the variable length coding.
2. Description of the Related Art
Many compression systems of an image and a sound adopt a system of performing the variable length coding of a signal processed using discrete cosine transform (DCT), and a representative one of such coding is Huffman coding. When a signal coded by Huffman coding is transmitted, the receiving side performs Huffman decoding of the transmitted signal by software or hardware. Because it takes a long processing time when the image size is large, the Huffman decoding is frequently realized by hardware.
There are currently a plurality of compression systems, and the number of the receivers, each supporting a plurality of compression systems, has increased. For example, a decoder of a next generation digital versatile disc (DVD), such as a HD-DVD and a Blue-ray Disc (registered trademark), must be able to expand all the compressed signals by MPEG-2, H.264, and VC-1. Incidentally, Huffman decoding is described in Japanese Patent Laid-Open Publication No. 2002-330076 and the like.
However, coding systems such as MPEG-2, MPEG-4 part 2, H. 264, and VC-1 severally assign a code peculiar to each coding form to the Huffman code used in the system. If a plurality of Huffman decoders are mounted in a receiver, the receiver must have decoding tables dealing with the respective coding systems because the respective coding systems have different coding tables. Consequently, the receiver has a problem of increasing the circuit size thereof.